Electromagnet with adjustable air gap



Sept. 22, 1964 R. w. KANE ETAL 3,150,295

ELECTROMAGNET WITH ADJUSTABLE AIR GAP Original Filed March 19, 1954 3 Sheets-Sheet 1 L. S Q; Q h Q) Q H w --I r z M w I H b l Inn. A h a Q l1 WT .J I o 1,.) ml Q i W a 2 m r a v 1|! a J N "In" I a g m t u 2 H N I N H w RALPH W- KANE FoeeesrAA/znsou EMEEV H. Bosses lAlllA/I'DRS ari 'gf MM Sept 22, 1954 R. w. KANE ETAL ELECTROMAGNET WITH ADJUSTABLE AIR GAP Original Filed March 19, 1954 5 Sheets-Sheet 2 E M V 12-3;- b & ML! vw 4 N mm 1 mm mm W .k km wm m N a v N ww R w m K 5 Nu W EAL/ H W. KANE Fo/eessr A.NE1-$ EMEEY H. Passes nvvewroes Sept. 22, 1964 R. w. KANE ETAL 3,150,295

ELECTROMAGNET WITH ADJUSTABLE AIR GAP Original Filed March 19, 1954 3 Sheets-Sheet 3 I x I\\\ EAL/ H W. KANE Foe/e as rA NELSON EMEEY H. Ease-Es IN VEN T 0R5 BY u United States Patent 3,150,295 ELECTROMAGNET WITH ADJUSTABLE AIR GAP Ralph W. Kane and Forrest A. Nelson, Atherton, and Emery H. Rogers, Palo Alto, Calif., assignors to Varian Associates, San Carlos, Califi, a corporation of California Original application Mar. 19, 1954, Ser. No. 417,482, now Patent No. 3,017,544, dated Jan. 16, 1962. Divided and this application Jan. 15, 1962, Ser. No. 174,332 Claims. (Cl. 317-158) This invention relates in general to magnets and more particularly to a novel magnet structure which provides extensive versatility in operation while maintaining precision and stability.

The present application is a divisional application of the parent application Serial No. 417,482, filed March 19, 1954, in the names of the same inventors, said application now being Patent 3,017,544 issued January 16, 1962.

In many applications of permanent and electromagnets there has long existed the need for an instrument in which the magnet gap spacing may be readily varied for controllably varying field strength and gap room and in which precise parallelism of the pole faces may be maintained so as to retain maximum field uniformity. Also, it is desired that pole pieces of varied sizes and configurations may be interchangeably utilized so as to regulate gap spacing, field strengths, and/ or field patterns, and in which the physical position of the magnet structure may be easily changed relative to the surroundings without undue exertion so that the magnet portions such as the gap may be made more readily accessible.

It is, therefore, an object of the present invention to provide a versatile magnet structure which will meet the above requirements without sacrificing the precision or stability obtainable in rigidly fixed magnet structures of relatively limited versatility.

One feature of the present invention is the provision of a novel magnet apparatus wherein the pole pieces are slidably mounted in sleeves secured in the yoke, the gap being variable by sliding the pole pieces back and forth in the sleeves.

Another feature of this invention is the provision of a novel shimming means for tilting the pole faces into parallelism.

These and other objects, features, and advantages of the present invention will be evident upon a perusal of the following specification and claims taken in connection with the accompanying drawings wherein,

FIG. 1 shows in plan view one embodiment of the novel magnet structure of the present invention,

FIG. 2 is an end view from the right of the magnet structure shown in FIG. 1,

FIG. 3 is a longitudinal cross section view of the magnet apparatus of FIG. 1,

FIG. 4 is an enlarged fragmentary section view of that portion of the magnet circled by line 4-4 in FIG. 3 showing the novel Rose shim construction,

FIG. 5 is an end view of the apparatus of FIG. 4,

FIG. 6 is a section view of another embodiment of the novel shimming apparatus,

FIG. 7 is an enlarged fragmentary section view of a portion of the magnet apparatus of FIG. 3 indicated by section line 7-7, and

FIG. 8 is a longitudinal section View of the gap-adjusting magnet embodying the present invention.

Referring now to the drawings, especially FIGS. 1, 2 and 3, there is shown an electromagnet which embodies certain novel features of this invention. This electromagnet comprises a yoke structure including two separable U-shaped yoke halves 1 and 2 which are arranged for relative axial movement to vary the magnet gap,

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yoke half 1 moving relative to the remainder of the magnet structure. The opposed surfaces of the legs of the yoke halves 1 and 2 are carefully machined to insure parallelism and proper contact. Yoke 2 is rotatably mounted by means of a hub portion 3 in the bore of a trunnion 4, the trunnion being mounted on a solid support or base 5 as by screws 6. Integral with the two leg portions of yoke half 2 are mounting bosses or protrusions 7, 8 and 9, these protrusions having cylindrical bores extending therethrough.

Rotatably mounted in the opposite trunnion 11 is an elongated bracket 12 having bores in the opposite ends thereof. A pair of partially threaded support rods 13 and 14- are fixedly mounted in the bores in said bracket by means of their turned down ends and jamming nuts 15 and 16. The opposite ends of these support rods 13 and 14 are fixedly secured within the bores of the protruding portions 7 and 9, respectively, as by pins 7' and 9, the rod 14 also extending through boss 8. The yoke half 1 also has bosses or protruding portions 17, 18 and 19 each having bores therethrough, said support rods 13 and 14 passing through the bores in said portions 17 and 18 and 19, respectively. The weight of the yoke halves and associated apparatus is carried by the two trunnions 4 and 11, the bracket 12 and the support rods 13 and 14.

Mounted on the support rod 13 on opposite sides of protrusion 17 are threaded nuts 21 and 22. Mounted on support rod 14 between protrusions 18 and 19 is a threaded nut 23. The yoke half 1 may be moved toward or away from the yoke half 2 by means of the nuts 21, 22 and 23. By backing nuts 21 and 23 from the portions 17 and 18 and by subsequently turning nuts 22 and 23 in engagement with the protrusions 17 and 19, the yoke 1 may be moved away from yoke 2 and in a similar reverse manner the yoke 1 may be moved toward yoke 2. With the yoke split, suitable yoke spacers 26 may be inserted between the yoke halves such that when the halves are again brought toward each other, the spacers are compressed in the yoke and maintain the field gap space at any desired length dependent on the size of the selected yoke spacers while at the same time completing the core path around the gap space. The yoke spacers 26 are carefully machined so that true parallelism of the pole faces is maintained throughout the range of gap spacings.

The rectangular yoke spacers are slightly wider than the yoke halves (see FIG. 7) and thus extend out from both sides of the yoke, the protruding portions of the spacers having aligned bores therein. Extending from both sides of the four yoke legs are small integral mounds or bosses 24, these mounds having narrow channels therein for accommodating spacer supporting rods 25. These rods 25 extend through the bores in the rectangular shaped yoke spacers 26, the bores and mounds 24 being so arranged that the rods are held in a bowed tension bearing against the mounds 24 whereby the spacers 26 are held fixedly in place between the yoke halves 1 and 2 while the yoke is split until the yoke half 1 may be moved toward yoke half 2 to compress the yoke spacers 26 therebetween.

Fixedly secured on the yoke halves 1 and 2 as by means of screws 27 are pole pieces 28 and 29, respectively. Slipped over these pole pieces 28 and 29 are the energizing coils 31 and 32, respectively, the coils being secured to the yoke halves by means of protruding tabs 33 and screws 34. Removable substantially cylindrical pole caps 35 and 36 are secured against the pole pieces 28 and 29 by means of draw bars or rods 37 and 38, respectively. Draw bar 37 is threaded at one end into a threaded bore in the inner surface of pole cap 35, this draw bar extending through cylindrical bores in the pole piece 28 and yoke half 1. The outer end of the draw bar is turned down and threaded at the extreme outer end thereof. The outer end 39 of the bore in the yoke 1 is threaded and a pole cap locking screw 41 is threaded into this bore. A cap nut 42 is securely tightened over the threaded end of the draw bar 37. To draw the pole cap 35 tightly against the pole piece 28, the pole cap lock screw 41 is turned out from the yoke, bearing against the cap nut 42 and thus forcefully moving the draw bar 37 to the right as viewed in FIG. 3 and thus pressing the pole cap 35 against the pole piece 28. The apparatus for securing pole cap 36 to the associated pole piece 29 is the same as described above for pole cap 35.

In utilizing this magnet it can be seen that the air gap between the pole caps 35 and 36 may be varied by replacing the pole caps with caps of a different thickness and shape or it may be varied by separating the two yoke halves 1 and 2 and changing the thicknesses of the yoke spacers between the two halves or a combination of these two methods may be used. The spacer rod 25 assures that the yoke halves may be split apart without having the spacers fall from between them, yet providing that the spacers may be easily and rapidly removed and replaced with other yoke spacers.

Also, because of the novel mounting structure for this split yoke type magnet, the whole magnet may be rotated about its longitudinal axis in the bores of the trunnions 4 and 11 through any desired angle, such as 90 as shown in FIG. 2.

A typical magnet made in accordance with the present invention has a pole diameter of 6 inches, pole caps of 6 inch diameter and 2 inch thickness. The minimum air gap is .25 inches and the maximum air gap with the yoke halves split apart is 6 inches. By use of various sized yoke spacers, the air gap is varied between the maximum and the minimum in steps of .25 inch.

This novel magnet structure, in addition to providing removable pole caps, also provides a novel method and apparatus for shimming the pole faces whereby various modifications of the magnetic field strength and pattern across the air gap may be obtained. The particular shimming employed is of the Roue shim type where the circumferential edge of the pole face is raised slightly to provide a raised annular band with respect to the main portion of the pole face. In a known method for producing a Rose shim of this type, the inner diameter portion of the face is turned down so as to leave the raised annular band portion around the circumference of the face. This method is not satisfactory because of the extreme dir culty in getting a true surface flatness of the turned down surface portion. One embodiment of the Rose shimmed pole face of the present invention is shown in FIGS. 3, 4 and and is produced by turning down the outer periphery of the pole caps 35 and 36 so as to produce annular recesses or steps around the pole caps. An annular member 46 is then machined to snugly fit within each annular recess portion and is secured to the pole cap by means of screws 47. The face of main pole cap such as 36 and the annular ring portion 46 may then be surface ground together to produce the true surface flatness needed for the main pole face and shim surfaces. The shimming of this annular ring 46 is then accomplished by placing an annular member 48 of shim material of any desired thickness, for example, 5 mils, under the annular member 46 and tightening the screws 47 to compress the shim 48 between the annular member and the ledge of the recess in the main pole cap. The shim 43 is compressed completely fiat with complete elimination of buckling regardless of the thinness of the shim material. If an attempt were made to secure such thin shims directly on the pole face surface, buckling of the shim would destroy any benefits derived from the shimming. But by compressing the shim material between two solid, unyielding members 36 and 46, this difiiculty is eliminated. Thus the height of the annular member 46 with respect to the main pole face may be of any desired value from zero on up in steps of thousands of an inch without affecting the parallelism of the faces of the member 46 and the main pole cap 36.

There is shown in FIG. 6 another embodiment of the novel pole shimming means where the pole caps 51 are tapered to a smaller diameter, the annular member 52 being tapered to conform to the tapered surface of the pole cap. A thin shim 52' is secured between the pole cap 51 and the member 52.

Shown mounted on the yoke half 1 in FIG. 2 is the manifold 49 and associated copper tubing 49 which carries cooling liquid such as water through the coil portion of this magnet for maintaining the magnet at a cool operating temperature.

In FIG. 8 is shown a novel gap-adjusting electromagnet apparatus which comprises a U-shaped yoke 53 having aligned bores extending through the opposite legs thereof. Fixedly secured in these bores are cylindrical sleeves 54 and 55, the sleeves having annular flanges 54 and 55' on their outer ends. Extending through threaded bores in the flanges 54 and 55' are shimming screws 56, the ends of which bear against the surface of the legs of the yoke 53. A plurality of these shimming screws are equally spaced around the flanges 54 and 55' and, by turning these screws in or out, the sleves 54 and 55 may be slightly tilted in the yokes in any direction relative to the longitudinal axis and in this manner the associated pole faces may be adjusted to the desired parallelism. Mounting screws such as 57 secure the flanged sleeves to the yoke. Extending within the sleeves are pole pieces 58 and 59, the outer ends of which are threaded. Captured adjusting nuts 61 and 62 are threaded over these ends of the pole pieces, the nuts being held captured by the annular members 63 and 64 which are fastened to the flanges 54' and 55' by the screws 57. The adjusting nuts 61 and 62 may be rotated to cause the pole pieces 58 and 59 to slide within the sleeve in either direction and thus vary the gap spacing between the poles.

The magnet coils 68 and 69 are slipped over the sleeves 54 and 55, respectively, and are secured to the yoke 53 by suitable means not shown. The coils are thus fixedly secured to the magnet structure yet the associated pole pieces are secured to the magnet structure so as to be movable with respect to the coils, thus permitting rapid adjustment of the magnet gap by movement of the pole pieces without movement of the heavy coils.

A key and keyway 65 prevent rotation of the pole pieces. The pole caps 66 and 67 are secured to the pole pieces 58 and 59 in the same manner as those in FIG. 3.

Since many changes could be made in the construction of the novel magnet invention described above and many apparently widely different embodiments of this invention could be made Without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. An electromanget comprising a substantially U- shaped yoke, the two legs of which have mutually aligned bores therethrough, a pair of hollow, cylindrical, openended sleeves extending through the bores, a pair of energizing coils each secured over an associated one of said sleeves, a pair of cylindrical pole members extending through the sleeves and forming an air gap between their inner ends, the outer ends of the pole members being threaded, adjusting nuts threaded over the outer ends of the two pole members, means for securing said adjusting nuts to said yoke whereby said adjusting nuts may only move rotatably with respect to said yoke, said rotatable movement of said adjusting nuts causing said pole members to slide in and out of said sleeves whereby said air gap spacing may be varied.

2. An electromagnet comprising a yoke including two opposed sides which have mutually aligned bores therethrough, a pair of hollow, cylindrical sleeves extending through the bores, a pair of energizing coils each secured over an associated one of said sleeves, a pair of cylindrical pole members extending through the sleeves and forming an air gap between their inner ends, and means for adjustably sliding said pole members within said sleeves whereby the size of the air gap may be varied.

3. An electromagnet comprising a yoke including two 5 opposed sides which have mutually aligned bores therethrough, a pair of hollow, cylindrical sleeves extending through the bores, a pair of energizing coils each secured over an associated one of said sleeves, a pair of cylindrical pole members extending through the sleeves and forming an air gap between their inner ends, means for adjustably sliding said pole members within said sleeves whereby the size of the air gap may be varied, and means for adjustably securing said sleeves within said yoke whereby said sleeves and associated pole members may be tilted within the yoke to adjust the parallelism of the inner ends of the two pole members.

4. An electromagnet as claimed in claim 3 wherein said last means comprises screw means for tilting and locking said sleeves within the associated bores in said yoke.

5. An electromagnet as claimed in claim 3 wherein said last means comprises a flange on the outer end of each sleeve, a plurality of shimming screws threaded through the flanges and engaging the yoke, and a plurality of mounting and locking screws extending through the flange and threaded into the yoke member.

References Cited in the file of this patent UNITED STATES PATENTS 2,819,431 Maxwell J an. 7, 1958 

1. AN ELECTROMAGNET COMPRISING A SUBSTANTIALLY USHAPED YOKE, THE TWO LEGS OF WHICH HAVE MUTUALLY ALIGNED BORES THERETHROUGH, A PAIR OF HOLLOW, CYLINDRICAL, OPENENDED SLEEVES EXTENDING THROUGH THE BORES, A PAIR OF ENERGIZING COILS EACH SECURED OVER AN ASSOCIATED ONE OF SAID SLEEVES, A PAIR OF CYLINDRICAL POLE MEMBERS EXTENDING THROUGH THE SLEEVES AND FORMING AN AIR GAP BETWEEN THEIR INNER ENDS, THE OUTER ENDS OF THE POLE MEMBERS BEING THREADED, ADJUSTING NUTS THREADED OVER THE OUTER ENDS OF THE TWO POLE MEMBERS, MEANS FOR SECURING SAID ADJUSTING NUTS TO SAID YOKE WHEREBY SAID ADJUSTING NUTS MAY ONLY 